This invention relates to a method of making a pipe fitting and, more particularly, to a fitting having a generally T-shape. In equipment using coils (either for heating or cooling), it has been the practice to utilize return bends to connect various rungs of piping and, in some instances a generally T-shaped fitting to connect three pipes or tubes, the T-shaped fitting approximating the appearance of a tripod. The simplest way of making such a tripod fitting was to braze an ell to a return bend or U-shaped fitting. However, this procedure resulted in many tripods which were faulty, particularly at the line of union. It was therefore felt that a superior product could be achieved through extruding or swaging a unitary piece in accordance with the well known procedure set forth in a Seeber et al U.S. Pat. No. 2,111,695 or utilizing hydraulic fluid as taught in Tadokoro U.S. Pat. No. 3,681,960. Use of these prrocedures resulted in an unsatisfactory product characterized by bursting, imperfect walls or wrinkling.
I have found that a suitable tripod fitting can be fabricated so as to have the benefit of a unitary fitting, i.e., no burrs at the joint to impede flow, through the use of a procedure wherein a solid plug or capsule of malleable metal is cold-worked or deformed to provide a tube closed at one end and further characterized by having a wall thickness adjacent that end greater than the wall thickness remote therefrom; and thereafter further deforming the tube to provide a pair of legs, i.e., a return bend adjacent that one end.
Other objects and advantages of the invention may be seen in the ensuring specification.